Examination of the spatial and temporal field distributions of single-cycle terahertz pulses at a beam focus

Measurements of spatially resolved beam profiles of single-cycle terahertz pulses are presented. In the approach here the terahertz beam is scanned over the stationary electro-optic detector using a gimbal-mounted mirror. A detailed study of the temporal- and frequency-dependent field in the region of the terahertz focus reveals field patterns which are dominated by diffraction and absorption. The observed field distribution is reproduced in model calculations. The exceptionally high signal to noise ratio and the high frequency and spatial resolution of the experiment here facilitate the observation of minute field distortions caused by the anomalous dispersion of absorbers in the beam path from the spatially resolved field pattern.